TURNING OR SHAVING (Pottery, for artists)
CHAPTER VII TURNING OR SHAVING "A sharp spear needs no polish." Zulu proverb. THE turning or shaving operation takes place when the green shape has dried to a leathery condi- tion. It consists in shaving the sides and hollow- ing the base until the thickness is uniform. The shape is thus made much lighter and rendered less liable to crack from unequal contraction. At the same time a fine finish is imparted to the surface. One of the handiest tools for shaving is shown in Fig. 27, no. 6, but a piece of hoop iron bent at right angles and shaped with a file will serve. Small hol- lows can be finished with a modelling tool. An old piece of leather will close up and finish the surface. In factories a horizontal lathe is usually employed, the shape being fitted over a chum or chuck. Skilled men can turn shapes down until they are scarcely thicker than tin, but this, it is needless to add, is an abuse of method even with porcelain, and quite out of place with stoneware or earthenware. All that is necessary is to trim the thick sides, hollow the base, and smooth the surface. (Fig. 35.) 73 .ACTION ./HEWING TURNED ^ THROWN WALL OF .A/HAPE A simple way to arrive at this is to throw on the wheel a chuck of stiff clay to fit the shape, wide- mouthed ones being fitted over and ordinary shapes within the chuck. (Figs. 36 and 37.) A piece of soft linen is placed over this chuck to pre- vent sticking and the shape fitted and centred. When spinning quite truly from right to left and steadied with the left hand, the tool should be gently applied as shown in the illustra- tion. Hollow the base and then shave the sides, turning all down very gradually and improve the outline as much as pos- sible in the process. Care must be taken with the base. If it is not quite true it should be sandpapered to stand flat. A little experience will soon show when it is in the best state for shaving. If the clay is too soft, the tool jumps, forming ridges, or possibly cuts deeply into the form. If it is too dry, the surface crumbles and the pot is liable to break. When turned in the right leathery condition, the shavings curl off like peel from an apple and all tool marks are FIG. 35 75 VING J3A5E< FIG. 36 76 easily removed. A beautiful finish may then be imparted with the leather. To end the process the shape is reversed in the chuck. Those most important parts, the shoulders and lip, are carefully rounded with a piece of felt and polished with the leather. Properly attended to, this will save much work and disappointment later on. Then with all holes filled up, all ridges, bumps, and sharp edges removed, the shape is signed and put to dry. For very delicate work in transparent glaze or under-glaze painting, the whole surface may be gone over with very fine sandpaper and polished with the hand. This may be done provided the body is a fine one, for with a coarse body this is apt to leave the surface looking gritty. Some little practice will be necessary in throwing stiff chucks and centring the shape securely, but this once mas- tered, the method here described will be found to be expeditious and satisfactory for turning shapes. A proper regard for process points to the desir- ability of leaving built shapes without a high finish. Yet they also, if built carefully and stoutly, may be turned down in the above manner. The building up and turning down is somewhat tedious, but it is sometimes the only way by which a craftsman can obtain large shapes. A rather more simple process is to centre the shape upon a whirler and 77 SHAVING THE 5IDE5 FIG. 37 turn down with a sharp wire tool, finishing off lightly with a sponge and soft leather. To accomplish this satisfactorily the shape must be fairly soft, as there can be no quick spinning motion to enable the tool to cut cleanly as in the chuck or the wheel. When the head of the whirler 78 OSITION OOL/ WHEN FIG. 38 is of plaster, it should be well soaked in water and the centred shape stuck down with soft clay. The hand holding the cutting wire tool must be held steady at a fixed distance from the centred shape and the pot may be sprayed with water blown through a diffuser from time to time, to keep it moist. Some clays will not, however, stand much re-wetting. It should not be necessary to caution the crafts- 79 man against angular profiles, splayed feet, or sharp mouldings. Such features are foreign to good pot- tery, however suited to metal or stone. With taste and judgement the irregular grooving caused by the tool can be made of high decorative value. In no case should the built shape try to masquerade as a thrown shape. When the whirler is used to shave down built shapes, they may be coiled very thick at the base, thus allowing more rapid work. The attention must then be concentrated on the profile of the inside. In this way many shapes that splay out or curve boldly from the foot may be built, which would otherwise present many diffi- culties in coiling. Categoría:Pottery, for artists, craftsmen & teachers